Colombo: Sri Lanka on Wednesday announced an investigation into claims that unidentified US politicians had received bribes to ensure Washington went soft on the island`s dismal human rights record.

Prime Minister Ranil Wickremesinghe said the new government would probe claims that large sums had been set aside to pay congressmen and other politicians by public relations firms hired by the previous regime.

"We want to know if US law too had been violated," Wickremesinghe told Parliament. "I am ordering the Foreign Ministry to make a thorough investigation and also inform the Americans about this."

Deputy Foreign Minister Ajith Perera said official records showed that unspecified sums had been claimed by lobby firms as payments to influence US representatives. No names were disclosed.

Sri Lanka had retained half a dozen lobbying firms to repair its image after a US-initiated resolution two years ago criticising the island`s rights record before, during and after the controversial crushing of separatist Tamil rebels in May 2009.

As international political pressure mounted on Colombo, the government last year secured a bipartisan resolution co-sponsored by 11 US senators asking President Barack Obama to adopt a "well-balanced policy" towards the island.

The new government of President Maithripala Sirisena, who defeated former strongman Mahinda Rajapakse, has sounded conciliatory and agreed to address international concerns over accountability for wartime abuses.

The new government has also cancelled all contracts with US lobbyists and vowed it will not outsource its diplomacy.

Last month the government cut ties with sex scandal-plagued former IMF chief Dominique Strauss-Kahn after paying him $750,000 for acting as an adviser to attract foreign investment.